Atlantic Oscillation (NAO) and the drought. In:
Assessment of the Regional Impact of Droughts in
Europe. Demuth, S. and Stahl, K.(eds). Final Report,
ARIDE. Institute of Hydrology, Freiburg, pp. 106–
ttir, J.F., Uvo, C.B. and Snorrason, A
Multivariate Statistical Analysis of Iceland River Flow
Series and Variability in Atmospheric Circulation. XXIII
Nordic Hydrological Conference, Tallinn, Estonia, 8–
12 August 2004. NHP Report 48,9985-56-921–0.
25. Snorrason, A
. 1990. Hydrological variability and
general circulation of the atmosphere. XVI Nordic
Hydrological Conference, NHK-90, Kalmar, Sweden,
29 July–1 August 1990.
26. Wedgbrow, C., Wilby, R.L., Fox, H.R. and O’Hare, G.
2002. Prospects for seasonal forecasting of summer
drought and low river flow anomalies in England and
Wales. Int. J. Climatol. 22, 219–236.
27. Wilby, R.L. 2001. Seasonal forecasting of UK river
flows using preceding North Atlantic pressure patterns.
J. Chartered Inst. Water Environ. Manage. 15, 56–63.
28. Wilby, R.L., Wedgbrow, C.S. and Fox, H.R. 2004.
Seasonal predictability of the summer hydrometeorol-
ogy of the River Thames, UK. J. Hydrol. 295, 1–16.
29. Kiely, G. 1999. Climate change in Ireland from
precipitation and streamflow observations. Adv. Water
Res. 23, 141–151.
30. Kaczmarek, Z. 2002. The influence of the North
Atlantic Oscillation on European river flow. In: The
North Atlantic Oscillation and Its Role in Climate and
Hydrology in Poland, 2002. Marsz, A.A. and Styszyn
ska, A. (eds.). Akademia Morska, Gdynia, pp. 163–172
31. Kaczmarek, Z. 2003. The impact climate variability on
flood risk in Poland. Risk Anal. 23, 559–566.
ska, A. 2002. Relationships between the Warta
River flow and winter NAO index in 1865–2000. In:
The North Atlantic Oscillation and Its Role in Climate
and Hydrology in Poland, 2002. Marsz, A.A. and
ska, A. (eds). Akademia Morska, Gdynia, pp.
173–180 (In Polish).
wka, D., Nieckarz, Z. and Pociask-Karteczka,
J. 2002. The North Atlantic Oscillation impact on
hydrological regime in Polish Carpathians. In: In-
terdisciplinary Approaches in Small Catchment Hydrol-
ogy: Monitoring and Research. FRIEND International
Conference, Demanovska Dolina, 25–28 September
2002, pp. 132–135.
34. Pociask-Karteczka, J., Limano
wka, D. and Nieckarz,
Z. 2002–2003. The North Atlantic Oscillation impact
on hydrological regime of Carpathian rivers (1951–
2000). Folia Geogr. Ser. Geogr. Phys. 33–34, 89–104 (In
Polish with English summary).
35. Pociask-Karteczka, J., Nieckarz, Z. and Limano
D. 2003. Prediction of hydrological extremes by air
circulation indices. Int. Assoc. Hydrol. Sci. Publ. 280,
36. Pfister, L., Humbert, J. and Hoffmann, L. 2002. Recent
trends in rainfall-runoff characteristics in the Alzette
River basin, Luxembourg. Climatic Change 45, 2, 323–
37. Stefan, S., Ghioca, M. and R^mbu, N. 2004. Study of
meteorological and hydrological drought in Southern
Romania from observational data. Int. J. Climatol. 24,
38. R^mbu, N., Boroneant, C., Buta, C. and Dima, M. 2002.
Decadal variability of the Danube River flow in the
lower basin and its relation with the North Atlantic
Oscillation. Int. J. Climatol. 22, 1169–1179.
39. R^mbu, N., Dima, M., Lohman, G. and Stefan, S. 2004.
Impact of the North Atlantic Oscillation and the El
o–Southern Oscillation on Danube River flow
variability. Geophys. Res. Lett. 31, 203–206.
40. Menduni, G., Baldi, M., Maracchi, G. and Meneguzzo,
F. 2004. The Arno River seasonal discharge as an index
of climate variability: trends and connections to the
larger scale variability. Geophys. Res. Abstr. 6.05257.
41. Rodriguez-Puebla, C., Encinas, A.H., Nieto, S. and
Garmendia, J. 1998. Spatial and temporal patterns of
annual preicipitation variability over the Iberian
Peninsula. Int. J. Climatol. 18, 299–316.
42. Trigo, R.M., Pozo-Vazques, D., Osborn, T.J., Castro-
Diez, Y., Ga
miz-Fortis, G. and Esteban-Parra, M.J.
2004. North Atlantic Oscillation influence on pre-
cipitation, river flow, and water resources in the Iberian
Peninsula. Int. J. Climatol. 24, 925–944.
43. Cullen, H.M. an d deMenocal, P.B . 2000. North
Atlantic influence on Tigris-Euphrates streamflow.
Int. J. Climatol. 20, 853–863.
44. Heidi, M., Cullen, H.M., Kaplan, A., Arkin, P. and
deMenocal, P.B. 2002. Impact of the North Atlantic
Oscillation on Middle Eastern climate and streamflow.
Climate Change 55, 315–338.
45. Rodwell, M.J., Rodwell, D.P. and Folland, C.K. 1999.
Oceanic forcing of the wintertime North Atlantic
Oscillation and European climate. Nature 398, 320–323.
46. Haarsma, R.J., Drijfhout, S.S., Opsteegh, J.H. and
Selten, F.M. 2000. The impact of solar forcing on the
variability in a coupled climate model. Space Sci. Rev.
Institute of Geography and Spatial
Department of Hydrology
Krakow, 30 387, Poland
Megacryometeors: Distribution on Earth and
The research of the historical record of ice
falls brings together many cases that are
apparently similar (1–3). Practically all
clear-sky ice falls were not appropriately
researched because they were routinely
assigned, without verification, to aircraft
icing processes, to wastewater from air-
craft lavatories (blue ice), or to the leakage
of aircraft water tanks. However, it is
important to take into account, first, that
documented historical references about
these events go back to the first half of
the 19th century, so many cases existed
before the invention of airplanes (1–3),
and second, that a detailed search of
scientific databases (Web of Science,
GeoRef) regardin g well-known a ircraft
icing processes revealed a lack of prece-
dents that corroborate that ice formation
on any part of aircraft can reach dimen-
sions of approximately 1 m and weights of
up to several hundred kilograms.
A simplistic analysis of these events as
a whole can thus lead to misunderstanding
because different types of ice falls corre-
spond to different formation scenarios in
the earth’s atmosphere, either natural in
the strict sense of the term, or with a direct
or indirect relation with human activities.
Consequently, it is necessary to define
differentiation criteria (e.g., texture, and
structural and compos itional character-
istics of the ice) to distinguish among them
(4). The term megacryometeor was recently
coined (5) for the following reasons: to try
to avoid terminological confusion; to
emphasize the existence of such atmo-
spheric phenomenon; and to describe large
atmospheric ice conglomerations that, de-
spite sharing many textural, hydrochem-
ical, and isotopic features detected in large
hailstones, are formed under unusual
atmospheric conditions that clearly differ
from those of the cumulonimbus cloud
scenario (i.e., clear-sky conditions).
The fall of large ice blocks (weighing
approximately 1 kg to hundreds of kilo-
grams) from the clear sky is one of the
most interesting (and controversial) issues
in the atmospheric sciences (6). Meaden
(6) used the term ice meteors to name them
and proposed that their origin had to be
different from that of large hailstones.
Later, Corliss (1) used the term hydro-
meteors. Corliss also differentiated them
from classic hailstones and suggested that
they have an atmospheric ori gin, but
different possible formation scenarios.
Probably the largest and most impressive
events of megacryometeors have occurred
in China, Brazil, and Spain. In 1995, an ice
block approximately 1 m in size fell in
Zhejiang, China (7). Some farmers wit-
nessed three large chunks of ice crash with
a whoosh into the paddies of Yaodou
village; the largest chunk left a crater
about a meter in diameter and a half-
meter deep. In Campinas and Itapira,
Brazil, two huge megacryometeors of 50
and 200 kg fell in 1997; the atmospheric
isotopic signature of both specimens was
unequivocally confirmed (8). Finally, on
21 July 2004, a huge mass of ice weighing
approximately 400 kg fell very close to
a 15-year-old girl in Toledo, Spain.
Our study of the rate of these earthfall
events indicates that mainly after 1950, the
number of hits has spectacularly increased,
and the hits occur over practically the
whole planet (3). From 2001 to April 2006,
a total of 46 ice-fall events have been
witnessed and recorded. Verifiable effects
include the megacryometeors’ crashing
through roofs or producing small impact
craters (i.e., La Milana, Soria, Spain, Fig.
1; Surrey, UK; Oakland, California, USA).
These impacts have occurred in Argentina,
Australia, Canada, Colombia, India, Ja-
pan, Mexico, New Zealand, Portugal,
Spain, Sweden, The Netherlands, the
United Kingdom, and the United States.
Fourteen ice falls occurred in 2005 alone;
these occurred in Japan, The Netherlands,
314 Ambio Vol. 35, No. 6, September 2006Ó Royal Swedish Academy of Sciences 2006